JP2000199843A - Step zoom lens camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lighten a burden imposed on control in focusing and adjustment, to make reliability high and to perform accurate focusing by providing adjusting areas where a focus lens group is simply to be moved in an optical axis direction without spoiling a focusing function on both sides of the respective steps of a cam groove. SOLUTION: The adjusting areas Z2a are provided at both ends of each step groove Z2-i (i=1 to 8), and a shifting area Z2b is provided between the adjusting areas Z2a. In the adjusting area Z2a, focusing operation in each step groove Z2-i is performed all the same even when adjustment is performed inside the adjusting area Z2a in order to obtain the moving amount of a two-group lens L2 consisting of a focusing factor. Since the adjusting areas Z2a where the focusing lens group is simply moved in the optical axis direction without spoiling the focusing function are provided on both sides of the respective steps of the can groove, the burden imposed on the control in the focusing and the adjustment is lightened, the reliability is made high and the accurate focusing is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a step zoom camera.

[0002]

2. Description of the Related Art Classic zoom lenses
In zooming, a plurality of zoom lens groups are moved along a predetermined zooming locus to change the focal length without moving the focus position, and in shutter release, the focus lens group is moved according to the subject distance. The focus lens group may be independent of the variable power lens group or may be common to any of the variable power lens groups. Such a classic zoom lens has been widely used for a mechanical zoom lens in which a cam ring having a cam groove is driven to rotate in a stepless manner manually or electrically.

On the other hand, a step zoom lens is
It is being adopted for a lens of a type that controls the rotation angle of a cam ring having a cam groove by pulse. This step zoom lens comprises: a. Dividing a cam groove formed in a cam ring into a plurality of steps from a wide end to a tele end, b. Setting the cam groove shape in each step so that the focus lens group also serving as a variable power lens group can focus on all object distances while performing a focusing operation with zooming; c. It is characterized in that pulse rotation is performed so that the rotation angle of the cam ring is focused on the basis of subject distance information in combination with the focal length existing in the step.

This step zoom lens stores a focusing table based on a combination of a subject distance and a focal length so that the rotation angle of the cam ring from the current position of the cam ring at the time of shutter release matches the subject distance. Since calculation can be performed, there is an advantage that focusing can be performed basically irrespective of the cam groove shape. For this reason, conventionally, the cam groove in each step has been formed linearly.

Also, since the rotation angle of the cam ring can be pulse-controlled, zooming adjustment (adjustment of the focus position at each focal length) and fb adjustment (adjustment of the focus position to the imaging plane (film plane) position) are also performed. There is also an advantage that it can be performed by setting (correcting) the rotation angle of the cam ring.

In this step zoom lens camera, when the cam ring is rotated in each step of the cam groove to focus on an object from the shortest photographing distance to infinity, the focal length also changes from the short focal length to the long focal point in each step. Change to distance. When the focal length changes, the focus sensitivity (the amount of change in the focus position when the focus lens group moves by a unit distance) naturally changes. As is well known, the focus sensitivity increases as the focal length increases, and the change in focus sensitivity with respect to the change in focal length is non-linear. Accordingly, if each step of the cam groove is linearly approximated, there is an advantage that machining is easy, but there is a problem that control becomes difficult and high-precision control cannot be performed. This problem will be described later.

[0007]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a highly reliable step zoom lens camera capable of reducing the control burden in focusing and adjustment and performing high-precision focusing. More specifically, it is an object of the present invention to improve the cam groove shape of a step zoom lens which has been conventionally linear.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a focus lens group which also serves as a variable power lens group which advances and retreats in the optical axis direction according to a cam groove formed in a rotationally driven cam ring, and a cam ring driving mechanism which pulse-controls the rotation angle of the cam ring. In the step zoom lens camera having a cam groove, the cam groove is displaced with respect to a non-linear virtual zooming trajectory that changes the focal length without changing the focus position, and a plurality of step portions dividing the wide end to the tele end into a plurality. Having;
Each step portion of the cam groove has a linear relationship between the rotation angle of the cam ring and the displacement amount of the focus lens group from the virtual zooming locus, and is itself a nonlinear shape, and has a focal length longer than the rotation of the cam ring. Focusing function when the focus lens group is moved to a position where it can focus on the subject from infinity to the shortest shooting distance while changing the cam ring rotation position on both sides. And an adjustment area for simply moving the focus lens group in the optical axis direction without impairing the image quality.

The cam ring adjustment area is used to give the cam ring a rotation angle for performing focus adjustment (zooming adjustment and fb adjustment).

The present invention can be generally applied to a step zoom lens camera having two or more variable-power lens units. In particular, the present invention has three variable-power lens units, and the intermediate two-unit lens is variable. When applied to a step zoom lens camera which is a focus lens group also serving as a doubler lens, a favorable effect can be obtained.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In this embodiment, as shown by a zoom locus in FIG. 1, a first group lens L1, a second group lens L2,
This is an embodiment in which the present invention is applied to a zoom lens in which the group lens L3 is a variable power lens group and the second group lens L2 also functions as a focus lens group. In order to simplify the description, the first lens group L1 to the third lens group L3 are guided straight in the optical axis direction, and the zooming cam grooves Z1 to Z3 of the first lens group L1 to the third lens group L3 are formed in a single cam ring. Suppose that. The rotational position of the rotationally driven cam ring is pulse-managed.

The zooming cam grooves Z1 and Z3 are defined as a zooming area (photographing distance ∞) from the wide end where the first lens group L1 and the third lens L3 are closest to the film surface (image pickup surface) to the telephoto end where they are farthest away. ) Has a trajectory that linearly increases or decreases the distance from the film surface (imaging surface). On the other hand, the zooming cam groove Z2 has a non-linear trajectory divided into eight steps of 1 to 8 within the zooming range from the wide end to the tele end. The divided step grooves of the zooming cam groove Z2 are referred to as step grooves Z2-i (i = 1 to 8) in order from the wide end. FIG.
There is a classic zooming trajectory, ie the shooting distance ∞
At this time, a virtual zooming locus Z2 ′ of the second lens group L2 that continuously changes the focal length without changing the focus position is drawn together with the first lens group L1 and the third lens group L3.

The step groove Z2-i can move the second lens unit L2 to the in-focus position of each subject between the infinity shooting distance (∞) and the shortest shooting distance (close) in each step. The trajectory is displaced with respect to the virtual zooming trajectory Z2 '. In the adjacent step,
The in-depth shooting distance (∞) and the shortest shooting distance (near) are reversed. As shown in detail in FIG. 2, the adjustment region Z2a is provided at both ends of each step groove Z2-i.
Are provided, and each step groove Z2-i (adjustment area Z2a) is provided.
, A transition zone Z2b is provided.

The role of the adjustment area Z2a is as follows.
The stop position of the cam ring is set in the step groove Z2-i according to the subject distance by design. However, the second lens unit L2 is provided with a focus adjustment (zooming adjustment and f
b) Depending on the factor, it is necessary to move the shutter softly at the time of shutter release, regardless of the subject distance (added to the subject distance). The adjustment area Z2a is set to secure the amount of movement of the second lens unit L2 due to the focus adjustment factor. That is, 2 by the focus adjustment factor
In order to obtain the amount of movement of the group lens L2, a step groove Z2-
Even if the end of i is moved (adjusted) in the adjustment area Z2a on both sides, the focusing operation in each step groove Z2-i can be performed in exactly the same manner. More specifically, referring to FIG. 2, the basic step groove Z2-1 is replaced with a step groove Z2-1 '.
The focusing operation can be performed in exactly the same manner even when the adjustment is made by using the adjustment area Z2a as in the case of the step grooves Z2-1 ″. The range (angle) is the same. The transition area Z2b is a cam groove that connects the adjacent step grooves Z2-i, and reverses the direction of the zooming cam groove Z2 so that each step groove Z2-i.
Is brought closer to the virtual zooming groove Z2 ′.

In the above cam structure, when the cam ring is rotated, the first lens group L1 and the third lens group L3 move by the zooming cam grooves Z1 and Z3, and at the same time, the second lens group L2 moves according to each step groove Z2-i. I do. At this time, the focal length changes within each step at the same time. However, it does not reach the focal length of an adjacent step. For example, the focal length at the shortest shooting distance in step 1 does not become the focal length at infinity shooting distance in step 2. Further, the cam ring does not stop in the transition zone Z2b.

In an actual lens barrel configuration, the zooming cam groove Z
Forming 1 to Z3 in a single cam ring has various disadvantages and restrictions. Therefore, it is preferable to form only the zooming cam groove Z2 in the cam ring. In FIG.
Cam ring 30 having only zooming cam groove Z2
Step groove Z2-i, adjustment area Z2a, transition area Z2
The example of the specific shape of b is shown.

In the present embodiment, on the basis of the above, the shape of the zooming cam groove Z2 (step groove Z2-i) is further considered. That is, each step groove Z2-i
Is characterized in that the rotation angle of the cam ring and the amount of displacement of the second lens unit L2 from the virtual zooming locus Z2 'have a linear relationship with respect to the non-linear virtual zooming locus Z2'. . Hereinafter, the reason and advantages will be described.

First, the principle of focus adjustment performed by software will be described. This is a two-group lens L of a three-group zoom lens
2 is an example in which focus adjustment is performed. In FIG. 9, when the zooming adjustment and the fb adjustment are performed by setting the rotation angle of the cam ring that drives the second lens unit L2 without mechanically performing,
The equivalent amount of zooming adjustment is Zadj, and the equivalent amount of fb adjustment is F
adj, where Adj is the amount of movement to be given to the second lens group L2 at the time of shutter release, it is given by Aadj = Zadj + Fadj.

The focus position before adjustment is p, the focus position Lw at the wide end and the focus position Lt at the tele end.
Is measured. Now, the focus sensitivity at the wide end (w), the intermediate focal length (i), and the tele end (t) are represented by Kw and K.
Assuming that i and Kt, Δpw = Kw × Zadj Δpi = Ki × Zadj Δpt = Kt × Zadj, Zadj = (Δpt−Δpw) / (Kt−Kw) = − (Lt−Lw) / (Kt−Kw) Fadj = Lw + pw = Lw-Kw (Lt-Lw) /
(Kt−Kw) Li = Fadj−Δpi = Lw + (Ki−Kw) (Lt−Lw) / (Kt−K
A), Aadj is: Aadj = −Li / Ki = − ｛Lw / Ki + (1−Kw / Ki) (Lt−Lw)
/ (Kt-Kw)}. Lw and Lt are measured values, and K
w, Ki, and Kt are values from lens data. Therefore, the rotation angle of the cam ring by Aadj at each focal length is stored, and the rotation angle of the cam ring based on the subject distance data is stored at the time of shutter release.
By adding the rotation angle of the cam ring by j, focus adjustment can be performed softly without performing mechanical focus adjustment.

On the other hand, in a step zoom lens which is an object of the present invention, particularly a zoom lens in which the first and third lens groups are also involved in the zooming operation, the focal length change based on the photographing distance in each step is large. The sensitivity change based on the focal length cannot be ignored. Therefore, as described above, the present invention adjusts the shape of each step groove Z2-i so that the rotation angle of the cam ring and the displacement amount of the second lens unit L2 from the virtual zooming locus Z2 'have a linear relationship. Before describing this relationship, a problem in the case where each step groove is linear (a cam groove (step groove) is represented by Z2h) will be described before describing this relationship. The relationship between the rotation angle (focal length) of the cam ring and the focus sensitivity is non-linear as shown in FIG. 10, but it can be approximated linearly within the divided steps.

FIGS. 5 to 7 show this comparative example. The definitions of the symbols (expressions) in FIGS. 5 to 7 are as follows. Section A: When the cam ring rotates in the telephoto direction, the second lens unit L2 moves the virtual zooming locus Z2 ′.
Step groove of the cam groove Z2h, which is separated from the front, B section;
When the cam ring rotates in the telephoto direction, the step groove of the cam groove Z2h where the second lens unit L2 approaches the virtual zooming locus Z2 ', y = f (x); an equation giving the virtual zooming locus Z2', y = aix + bi; section A Y = ajx + bj; equation giving cam groove Z2h in section B, x: cam ring rotation angle, y: position in the optical axis direction of second group lens L2, ai: cam groove Z2h in section A Slope, bi: intercept of cam groove Z2h in section A, aj: inclination of cam groove Z2h in section B, bj: intercept of cam groove Z2h in section B.

The fact that each step groove is linear indicates that the shape of the cam groove Z2h is linear. In this relationship, the rotation angle of the cam ring and the displacement amount of the cam groove Z2h from the virtual zooming locus Z2 ′ (that is, the second group lens L2
Y = f ′ (x), y = f ′ (x) plotting the difference between the cam groove Z2h and the virtual zooming locus Z2 ′.
−f ′ (x)) becomes non-linear.

Thus, the rotation angle of the cam ring and the cam groove Z
If the relationship with the displacement amount (displacement amount of the second lens unit L2) from the virtual zooming locus Z2 ′ of 2h is non-linear, the above-described focus adjustment amount is converted into the rotation angle of the pulse-controlled cam ring and given. Is complicated, not only takes a long time, but also lowers the accuracy. More specifically, this comparative example divides y = f ′ (x) and y = −f ′ (x) into short steps to obtain a rotation angle of the cam ring corresponding to the focus adjustment amount, and forms a straight line. This means that a step of approximating and obtaining the inclination in each divided area, and obtaining the rotation angle of the cam ring corresponding to the focus adjustment amount according to the inclination and the subject distance is required. This requires computation time,
The stop position of the second lens unit L2 is also incorrect.

FIGS. 2 to 4 show an embodiment of the present invention corresponding to the comparative example of FIGS. 5 to 7. FIG. The definitions of the symbols (expressions) in FIGS. 2 to 4 are as follows. In addition,
Descriptions of symbols (expressions) common to those in FIGS. 5 to 7 are omitted. y = f (x) + c (x-xi 1); wherein providing a cam groove Z2h in the section A, y = f (x) -c (x-xj 2); wherein providing a cam groove Z2h in the section B, c Inclination of displacement of cam groove Z2h from virtual zooming locus Z2 ', y = cx; displacement of cam groove Z2h from virtual zooming locus Z2' in section A, y = -cx; virtual zooming locus Z2 'in section B
Xi ₁ : cam ring rotation angle at infinity shooting distance in section A, xi ₂ : cam ring rotation angle at shortest shooting distance in section A, xj ₁ ; infinity shooting distance in section B Xj ₂ ; cam ring rotation angle at the shortest shooting distance in section B.

The features of this embodiment as compared with the comparative example are that the zooming cam groove Z2 is non-linear,
This non-linear shape depends on the rotation angle x of the cam ring and the cam groove Z2.
Is determined so as to be linear with respect to the displacement amount (displacement amount of the second lens unit L2) from the virtual zooming trajectory Z2 ′ (the relationship is y = cx or y = −cx). . In short, y = f ′ (x) and y = −f ′ (x) in the comparative examples of FIGS. 5 to 7 correspond to FIGS.
That is, the shape of the cam groove Z2 (step groove Z2-i) is set so that y = cx or y = −cx.

As described above, the cam groove Z2 (step groove Z2-
By setting the shape of i), the focus adjustment amount can be easily calculated from the rotation angle x of the cam ring. If the focus sensitivity at a position rotated by an angle θ from the reference angle in the i-step is Ki (θ), Ki (θ) = Ki + Gi × θ, where Ki; the reference sensitivity (here, ∞ the sensitivity at the shooting distance), Gi: slope of change in sensitivity, given by

Therefore, this Ki is calculated by the following equation of the focus adjustment amount: Aadj = − ｛Lw / Ki + (1−Kw / Ki) (Lt
By substituting into Ki of −Lw) / (Kt−Kw)｝, Aadj can be obtained, and the rotation angle Δθi of the cam ring required to obtain this Aadj can be obtained by Δθi = Aadj / c. it can. Therefore, at the time of shutter release, an amount obtained by adding the rotation angle Δθi based on the focus adjustment amount to the rotation angle of the cam ring based on the subject distance information is obtained.
What is necessary is just to rotate a cam ring.

The present invention can be applied to a general camera that performs step zooming by rotating the cam ring having the above-described zooming cam groove Z2 by pulse management, and its specific mechanism is not limited. Next, a mechanical configuration example applied to a three-unit zoom lens will be described.

As shown in FIGS. 11 to 14, the step zoom lens camera 5 includes a camera body 9 and a zoom lens barrel 10. An aperture plate 11 is fixed inside the camera body 9, and an edge of the aperture plate 11 on the optical axis O side forms an aperture 11 a that determines an exposure area to the film. At the front of the aperture plate 11, a fixed lens barrel 13 is fixed to the camera body 9.
A female helicoid 14 is formed on the inner peripheral surface of the fixed lens barrel 13, and a plurality of rectilinear guide grooves 15 parallel to the optical axis O are further formed on the inner peripheral surface of the fixed lens barrel 13. .

A cutout 13a is formed in the fixed lens barrel 13 in a direction parallel to the optical axis O, and a zoom gear (multiple pinion) 16 is attached to the cutout 13a. The zoom gear 16 is rotatably supported at a rotation center parallel to the optical axis O, and has a tooth surface of a pinion portion protruding from the cutout portion 13 a to the inside of the fixed lens barrel 13. A zoom motor M is provided in the camera body, and the rotation of the drive shaft of the zoom motor M is transmitted to the zoom gear 16 via the zoom gear train 8.

A slit disk 12a having a plurality of slits is fixed to the drive shaft of the zoom motor M.
The rotation of the slit disk 12a is controlled by the photointerrupter 1.
By detecting at 2b, the drive amount of the zoom motor M can be detected. Since the amount of extension and storage of the zoom lens barrel 10 depends on the amount of drive of the zoom motor M, the pulse detection mechanism 12 (see FIG. 15) including the slit disk 12a and the photo interrupter 12b is used. The rotation angle of the cam ring 30 described later can be pulse-controlled.

A male helicoid 18 formed near the rear end of the outer peripheral surface of the first outer cylinder 17 is screwed into the female helicoid 14 of the fixed lens barrel 13. The width of the male helicoid 18 in the direction of the optical axis is formed so as not to be exposed to the external appearance when the first outer cylinder 17 is fully extended. The first outer cylinder 17 further includes
A plurality of outer peripheral gear portions 19 parallel to the male helicoid 18 are provided on the same peripheral surface on which the male helicoid 18 is formed. The teeth of each of the outer peripheral gear portions 19 are formed in a direction parallel to the optical axis O, and the zoom gear 16 meshes with the teeth. Further, the optical axis O is provided on the inner peripheral surface of the first outer cylinder 17.
A plurality of rotation transmitting grooves 17a are formed in a direction parallel to the direction (only one is shown in the figure).

A first straight guide ring 20 is provided inside the first outer cylinder 17. The first rectilinear guide ring 20 has a pair of flange portions 2 parallel to the circumferential direction on the outer peripheral surface near the rear end.
1a and 21b are protruded outward in the radial direction, and a portion sandwiched between the pair of flange portions 21a and 21b is an annular groove 21c centered on the optical axis O. Meanwhile, the first
At the rear end portion of the inner peripheral surface of the outer cylinder 17, a plurality of engaging claws 23 are provided radially inward (on the optical axis O side) at different positions in the circumferential direction.
(Only one is shown in the figure). The thickness of each engagement claw 23 is such that it can fit in the annular groove 21c formed in the first rectilinear guide ring 20 without play in the direction parallel to the optical axis O and can slide in the circumferential direction. ing.
Therefore, when the engaging claw 23 is engaged with the annular groove 21c, the first outer cylinder 17 and the first rectilinear guide ring 20 are coupled so as to be relatively immovable and relatively rotatable in the optical axis direction.

A plurality of rectilinear guide projections 24 are provided on the rear end of the first rectilinear guide ring 20 at different positions in the circumferential direction so as to project radially outward. Each straight guide projection 2
Numerals 4 are slidably engaged with a plurality of rectilinear guide grooves 15 formed on the inner peripheral surface of the fixed lens barrel 13, respectively. Accordingly, the first rectilinear guide ring 20 is moved integrally with the first outer cylinder 17 in the optical axis direction, but the relative rotation with respect to the fixed lens barrel 13 is restricted in the circumferential direction around the optical axis O. ing. That is, the vehicle is guided straight ahead.

The first outer cylinder 17 and the first straight guide ring 20 described above.
Constitute the first extension step portion of the zoom lens barrel 10. When the zoom gear 16 is rotated in a predetermined lens feeding direction by the zoom motor M, the first feeding step portion rotates the first outer cylinder 17 via the outer peripheral gear portion 19, and the female helicoid 14 and the male helicoid 18 Depending on the relationship, the first outer cylinder 17 is extended from the fixed lens barrel 13 while rotating. at the same time,
Since the first rectilinear guide ring 20 and the first outer cylinder 17 are claw-engaged so as to be relatively rotatable, the first rectilinear guide ring 20 moves together with the first outer cylinder 17 while being rectilinearly guided with respect to the fixed lens barrel 13. Move in the optical axis direction.

On the inner peripheral surface of the first rectilinear guide ring 20, a female helicoid 27 having the same inclination direction as the female helicoid 14 is formed. The inner peripheral surface of the first straight guide ring 20 further includes:
A plurality of linear guide grooves 28 parallel to the optical axis O are formed at different positions in the circumferential direction.

A cam ring 30 having a male helicoid 29 screwed to the female helicoid 27 on the outer peripheral surface is provided inside the first rectilinear guide ring 20. The male helicoid 29 is formed on the entire outer peripheral surface of the cam ring 30. In addition, a male helicoid 2 is provided on the entire inner peripheral surface of the cam ring 30.
A female helicoid 31 is formed in a direction opposite to that of the female helicoid 9.
At the rear end of the inner peripheral surface of the cam ring 30, a plurality of engaging claws 32 (only one is shown in the drawing) are radially inward (on the optical axis O side) at different positions in the circumferential direction. ) Is protruding.

A second linear guide ring 33 is provided inside the cam ring 30. This second straight traveling guide ring 33 is
A pair of circumferentially parallel flange portions 34a, 34b is provided on the outer peripheral surface near the rear end so as to protrude outward in the radial direction. A portion sandwiched between the pair of flange portions 34a, 34b An annular groove 34c is provided at the center. A plurality of engaging claws 32 protruding from the inner peripheral surface of the cam ring 30 are fitted into the annular groove 34c, so that the cam ring 30 and the second
The rectilinear guide ring 33 is coupled so as to be relatively immovable and relatively rotatable in the optical axis direction.

At the rear end of the second straight guide ring 33, a plurality of straight guide projections 36 projecting radially outward are provided at different positions in the circumferential direction so as to project radially outward. Each of the rectilinear guide projections 36 is slidably engaged with a plurality of rectilinear guide grooves 28 formed on the inner peripheral surface of the first rectilinear guide ring 20. Therefore, the second rectilinear guide ring 33 cannot move relative to the cam ring 30 in the optical axis direction, and is guided rectilinearly to the fixed lens barrel 13 via the first rectilinear guide ring 20.

The second outer cylinder 40 covers the outer periphery of the cam ring 30 and is located between the first outer cylinder 17 and the first rectilinear guide ring 20. The second outer cylinder 40 has a plurality of rotating projections protruding from the outer peripheral surface near the rear end. The transmission protrusion 41 is slidably engaged with a plurality of rotation transmission grooves 17 a formed on the inner peripheral surface of the first outer cylinder 17 and extending in a direction parallel to the optical axis O. Therefore, the second outer cylinder 40 is guided relative to the first outer cylinder 17 so as not to rotate relative to the first outer cylinder 17 and to be relatively movable in a direction parallel to the optical axis O.

At the front end of the cam ring 30, a rib 37 having three notches 38 is protruded. In the second outer cylinder 40, three engagement claws 39 that can be fitted into the notches 38 are provided on the front end side of the inner peripheral surface so as to protrude radially inward at positions different in the circumferential direction. . The engaging claw 39 and the notch 3
8 and the decorative ring 42 is attached to the front end, so that the cam ring 30 and the second outer cylinder 40
They are integrally coupled so as not to move relative to each other in the direction of the optical axis and to rotate relative to each other. Therefore, the second outer cylinder 40 rotates according to the first outer cylinder 17, and applies a rotational force to the cam ring 30.

The above-described cam ring 30 and second straight guide ring 3
The third and second outer cylinders 40 constitute a second extension step portion of the zoom lens barrel 10. First outer cylinder 1 that constitutes the first feeding step portion
When the rotating member 7 is extended from the fixed lens barrel 13, the second outer cylinder 40 rotates together with the first outer cylinder 17 due to the relationship between the rotation transmitting groove 17 a and the rotation transmitting protrusion 41. Second outer cylinder 40
Due to the relationship between the female helicoid 27 and the male helicoid 29, the cam ring 30 receiving the rotation of the first outer cylinder 17 rotates together with the second outer cylinder 40 with respect to the fixed lens barrel 13 in the same direction as the rotation direction of the first outer cylinder 17. It is extended from one straight traveling guide ring 20. At the same time, since the second rectilinear guide ring 33 is relatively rotatably coupled to the cam ring 30, the rectilinear guide projection 36
Due to the relationship between the first straight guide ring 20 and the straight guide groove 28, the guide ring 20 moves in the optical axis direction together with the cam ring 30 while being guided straight by the first straight guide ring 20.

A third outer cylinder 45 is provided inside the cam ring 30.
Are arranged. The aforementioned second straight guide ring 33 is located inside the third outer cylinder 45. Second straight guide ring 33
A plurality of guide rails 33 are provided in parallel with the optical axis
a is formed. On the other hand, a plurality of guide rails 45a that engage with the guide rails 33a are formed on the inner peripheral surface of the third outer cylinder 45. The guide rails 45a provided on the third outer cylinder 45 are slidably engaged with the guide rails 33a provided on the second linear guide ring 33, respectively. Is guided so as to be relatively movable in a direction parallel to the optical axis O with respect to the second rectilinear guide ring 33.

A female helicoid 31 provided on the inner peripheral surface of the cam ring 30 is screwed into the rear outer peripheral surface of the third outer cylinder 45.
A male helicoid 46 is formed. When the cam ring 30 performs the feeding rotation, a rotational force is applied to the third outer cylinder 45, and the third outer cylinder 45 is guided straight by the second straight guide ring 33. Therefore, the third outer cylinder 45 is
During the rotation of the lens barrel 0, the fixed barrel 1 does not rotate integrally with the fixed lens barrel 1 due to the relationship between the male helicoid 46 and the female helicoid 31.
3 is fed out of the cam ring 30 while moving straight in a direction parallel to the optical axis O. That is, the third outer cylinder 45 constitutes the third extension step of the lens barrel, and the third helicoid 4
The width of 6 in the optical axis direction is set so as not to be exposed to the external appearance when the third outer cylinder 45 is fully extended.

The second straight guide ring 33 has three second straight guide slits 50 formed in a straight line parallel to the optical axis O by cutting a part of the peripheral surface. In the present step zoom lens camera 5, the cam groove for zooming in the third group is composed of two types of oblique grooves.
Three zooming cam grooves Z3a for three groups that are skewed with respect to the group straight guide slit 50 are formed. A group zooming cam groove Z3b is formed. Of these, the third group zooming cam groove Z3a is provided with a second straight guide ring 33.
Penetrates the inner peripheral surface and the outer peripheral surface.

As described above, the inner peripheral surface of the cam ring 30 has a non-linear shape itself, and the rotation angle of the cam ring 30 in each step and the virtual zooming locus Z.
Three two-unit zoom cam grooves Z2 whose shapes are set so that the displacement amount of the second lens unit L2 from 2 ′ has a linear relationship are formed. Zooming cam groove Z2 for 2nd group
Each step further has the above-described adjustment area on both sides of the photographing range.

The first lens frame 47 is provided inside the third outer cylinder 45.
Are fixed, and the first lens group L1 is held by the first lens frame 47. The first lens unit L1 includes a third outer cylinder 4
The movement locus of the first lens unit L1 when the third outer cylinder 45 advances and retreats in the optical axis direction along with the optical axis 5 is a linear zoom locus as shown in FIG. That is, in the present step zoom lens camera 5, the zoom cam groove (Z
Although 1) is not provided, it is as described above that the present invention does not ask about the driving mode of the first lens unit L1.

The second group unit 48 includes a second group lens frame 48a for holding the second group lens L2, and the second group lens frame 48a.
Is fixed to the shutter block 54,
Three slide plates 55 are provided at the rear end of the shutter block 54.
Extends rearward. Each slide plate 55
Are slidably guided by a second group straight guide slit 50 formed in the second straight guide ring 33. Further, a second group cam follower 56 projects radially outward from each of the three slide plates 55, and each second group cam follower 56 is engaged with a second group zooming cam groove Z <b> 2 formed in the cam ring 30. Therefore, when the cam ring 30 rotates,
The second group unit 48 performs a predetermined forward and backward movement in the optical axis direction according to the locus of the second group zooming cam groove Z2 while being guided straight.

The third group unit 49 has a third group lens L3 of three.
The third group support ring 49a has three extending plates 57 protruding forward. Each extension plate 57 is provided with a third group cam follower 58 which protrudes outward in the radial direction, and the third group cam follower 58 is provided with the third group zooming cam groove Z3.
a and is engaged with the third group zooming cam groove Z3b. With this structure, when the cam ring 30 rotates, the third group cam follower 58 is guided by the combined locus of the zooming cam grooves Z3a and Z3b, and the third group unit 49
Moves along a linear trajectory as shown in FIG. 1 in the optical axis direction.
Since the cam grooves Z3a and Z3b are each formed obliquely with respect to the optical axis, the third group unit 49 moves back and forth in a direction parallel to the optical axis with a rotation operation about the optical axis O.

A compression spring 59 for removing backlash is disposed between the second group unit 48 and the third group unit 49. The second group unit 48 is located forward in the optical axis direction, and the third group unit 49 is located in the optical axis direction. It is urged to move backward.

The focal length of the zoom lens system is the first outer cylinder 1
The brush 62 fixed to 7 and the sliding contact relationship between the zoom code plate 63 affixed to the outer peripheral surface of the first rectilinear guide ring 20 can be detected as distance information of a finite number of steps.
The zoom code plate 63 and the CPU 70 are connected via the FPC board 60, and the first outer cylinder 17 and the first straight guide ring 2
The zoom code plate 63 and the brush 62 according to the relative rotation of 0
Is changed, the focal length (step) is detected. As shown in FIG. 16, the code pattern of the zoom code plate 63 is formed so as to be electrically connected to the two contacts of the brush 62 every time the rotation angle of the first outer cylinder 17 and the first straight guide ring 20 changes by a fixed angle. Thus, the focal length in eight steps from 1 to 8 can be detected.

As shown in FIG. 15, the step zoom lens camera 5 further includes a zoom operating means 64, a shutter release means 65, a distance measuring means 66, and a light measuring means 67, and each means is connected to the CPU 70. . The zoom operation means 64 gives a zooming command to the zoom lens barrel 10, that is, a command to move from the wide side to the tele side, and a command to move from the tele side to the wide side, and is composed of, for example, a momentary switch. The shutter release means 65 is composed of a release button, and gives a distance measurement command to the distance measurement means 66 and a light measurement command to the photometry means 67 by pressing the shutter button one step, and operates the shutter block 54 by pressing the shutter button two steps. . The shutter block 53 receives a photometric output from the photometric means 67 and opens a shutter blade (not shown) for a predetermined time. Further, a ROM (EEPROM) 68 connected to the CPU 70 is provided.

The ROM 68 stores the infinity shooting distance (∞) to the shortest shooting distance (close) in each focal length step.
The rotation angle (focusing table) of the cam ring 30 for moving the second lens unit L2 to the in-focus position for the subject during the period is stored in advance.

Further, in the ROM 68, the above equation for obtaining the focus adjustment amount (Aadj) within each focal length step is obtained. Aadj = -ａｄLw / Ki + (1-Kw / Ki) (Lt
−Lw) / (Kt−Kw)} and the above-mentioned expression representing the rotation angle of the cam ring 30 for performing the focus adjustment, Δθi = Aadj / c, is written in advance. At the time of assembling the camera, if the focus positions Lw and Lt at least at the wide end and the tele end are measured and written into the ROM 68, the rotational angle of the focus adjustment cam ring 30 at each focal length can be obtained from the above two equations. The rotation angle (focus adjustment table) of the focus adjustment cam ring 30 thus obtained is stored in the ROM 68.

The zoom lens system of the step zoom lens camera 5 operates as follows. When the zoom motor M is driven in the extending direction from the lens barrel storage state of FIG. 11 or the wide end of FIG.
The first straight guide ring 20 moves forward together with the first outer cylinder 17 while being guided straight by the fixed lens barrel 13. Then, together with the second outer cylinder 40, the cam ring 3
While 0 rotates in the same direction as the rotation direction of the first outer cylinder 17,
It is fed out from the first straight guide ring 20. At the same time, the second straight guide ring 33 moves straight in the optical axis direction together with the cam ring 30, and the third outer cylinder 4 guided straight by the second straight guide ring 33.
5 moves forward in the optical axis in response to the rotation of the cam ring 30, and the first lens unit L1 fixed to the third outer cylinder 45 moves linearly forward in the optical axis. At this time, the second straight guide ring 3
3 and a third group zooming cam groove Z formed in the third outer cylinder 45.
By the guidance of 3a and Z3b, the third lens unit L3 is also moved in a linear locus forward of the optical axis. The second lens unit L2 is
Zooming cam groove Z2 for second group formed on cam ring 30
As a result, it moves in the direction parallel to the optical axis along the non-linear movement locus shown in FIG. When the zoom motor M is driven in the storage direction from the telephoto end in FIG. 13, the zoom lens barrel 10 and each of the lens units L1 to L3 operate in the opposite direction to the time when the lens barrel is extended.

The focusing operation at each focal length is controlled as follows. When the zoom operation means 64 is operated, the brush 62 and the zoom code plate 63 are brought into sliding contact with each other, and one of the focal length steps 1 to 8 is detected. In each step, a point in time when the brush 62 and the zoom code plate 63 come into contact with each other when the lens barrel is extended from the storage (wide end) side is used as a pulse count reference. Although not shown, since the step zoom camera 5 has a finder optical system in addition to the photographing optical system, it is not necessary to move the second lens unit L2 to the in-focus position at the time of the zoom operation. Therefore, when the operation of the zoom operation unit 64 is released, the zoom lens barrel 10 stops at the standby position in the lens barrel storage direction from the pulse count reference position in each step.

In this standby state, when the release button is half-pressed and the distance measuring operation by the distance measuring means 66 is performed, C
The PU 70 detects the subject distance. Then, the rotation angle of the cam ring 30 for moving the second lens unit L2 to the position where the subject is focused is read from the focusing table stored in the ROM 68. Further, the rotation angle of the focus adjustment cam ring 30 at this focal length step is also read from the focus adjustment table of the ROM 68, and the final rotation angle (stop position) of the cam ring 30 is determined together with the data from the focusing table. Desired. The obtained rotation angle position is compared with the rotation angle position of the cam ring 30 at the pulse count reference position, and the drive pulse of the zoom motor M necessary to drive the cam ring 30 from the reference position to the determined rotation angle position is obtained. The calculation is performed by the CPU 70.

When the release button is fully depressed and an ON signal is input from the shutter release means 65, the zoom motor M is driven to operate the zoom lens barrel 10 in the extending direction, and the brush 62 and the zoom code plate are moved. The pulse count of the zoom motor M is started from the contact point 63, that is, from the reference position. When the previously calculated pulse number is detected, the zoom motor M is stopped, and the second lens unit L2
Is held at the position where focusing and focus adjustment have been performed. After photographing, the zoom lens barrel 10 returns to the above-described standby position for each step. In this way, it is possible to cause the second group lens L2 to perform a focusing operation with soft focus adjustment. In the present embodiment, the above-described focusing operation is performed at the time of shutter release.
The driving form of the focusing is not limited to this. For example, the focus lens group may be moved to the in-focus position when the distance measurement is completed. Further, the standby position of the zoom lens barrel in each step may be different from the embodiment.

As described above, in the above-described focusing control, the shape of the zooming cam groove Z2 for the second group has a linear relationship between the rotation angle of the cam ring 30 and the displacement of the second group lens L2 from the virtual zooming locus Z2 '. The rotation angle of the cam ring 30 to be pulse-controlled can be determined by a simple calculation. Further, since each step portion of the zooming cam groove Z2 for the second group has an adjustment area, it is possible to cope with a case where the focus adjustment amount is large and the determined rotation angle goes out of the normal shooting range.

[0060]

As described above, according to the present invention, the cam groove shape of the step zoom lens, which has been linear in the conventional step, is changed to the rotational angle of the cam ring and the displacement amount of the focus lens group from the virtual zooming locus. In order to make a linear relationship, it is improved to a non-linear shape by itself, and an adjustment area is provided on both sides of each step of the cam groove, which simply moves the focus lens group in the optical axis direction without impairing the focusing function. Therefore, it is possible to obtain a highly reliable step zoom lens camera capable of reducing the burden of control in focusing and adjustment and performing highly accurate focusing.

[Brief description of the drawings]

FIG. 1 shows a step zoom lens camera according to the present invention.
It is a figure showing the example of a zooming locus (cam groove shape) at the time of applying to a group zoom lens.

FIG. 2 is an enlarged view of a part of a locus of a zooming locus of FIG. 1 for a two-unit lens (a variable-magnification lens group and a focus lens group).

FIG. 3 is a graph illustrating a locus for a second group lens in FIG. 2;

FIG. 4 is a graph illustrating a locus for a second group lens in FIG. 2;

5 is a locus diagram for a second group lens corresponding to FIG. 2 and shown as a comparative example.

FIG. 6 is a graph illustrating the trajectory for the second group lens in FIG. 5;

FIG. 7 is a graph illustrating the trajectory for the second group lens in FIG. 5;

FIG. 8 is a development view showing a specific example of a cam ring having a cam groove for a second group lens.

FIG. 9 is a diagram illustrating zooming adjustment performed in a software manner by a cam ring whose rotation angle is pulse-managed.

FIG. 10 is a graph showing an example of the relationship between the rotation angle of a cam ring and the focus sensitivity of each lens group.

FIG. 11 is an upper half sectional view showing a specific mechanical configuration when a step zoom lens camera according to the present invention is applied to a three-unit zoom lens, in a state where a zoom lens barrel is housed.

FIG. 12 is a side sectional view at a wide end of the zoom lens barrel in FIG. 11;

13 is a side sectional view of the zoom lens barrel shown in FIG. 12 at a telephoto end.

FIG. 14 is an exploded perspective view of a zoom lens barrel.

FIG. 15 is a block diagram showing a control circuit system of the step zoom lens camera whose mechanical configuration is shown in FIGS. 11 to 14.

FIG. 16 is a development view showing an example of a focal length detection mechanism of the step zoom lens camera.

[Explanation of symbols]

 Reference Signs List 5 step zoom lens camera 9 camera body 10 zoom lens barrel 13 fixed barrel 12 pulse detection mechanism 17 first outer cylinder 20 first straight guide ring 30 cam ring 33 second straight guide ring 40 second outer cylinder 45 third outer cylinder 56 second group cam follower 58 third group cam follower 62 brush 63 zoom code plate 64 zoom operating means 66 distance measuring means 68 ROM 70 CPU L1 first group lens L2 second group lens L3 third group lens M zoom motor Z1 zooming cam groove (for first group) Z2 Zooming cam groove (for 2nd group) Z2 'Virtual zooming locus Z3 (Z3a, Z3b) Zooming cam groove (for 3rd group)

Claims (3)

[Claims] 1. A focus lens group, which also functions as a variable power lens group, advances and retreats in an optical axis direction according to a cam groove formed in a rotationally driven cam ring; the cam groove changes a focal length without changing a focus position. It has a plurality of steps divided from the wide end to the tele end, which are displaced with respect to the non-linear virtual zooming locus; each step of the cam groove has a rotation angle of the cam ring and a focus from the virtual zooming locus. The lens has a linear relationship with the amount of displacement of the lens group.The lens itself has a non-linear shape, and the focus lens is located at a position where it can focus on the subject from infinity to the shortest shooting distance while changing the focal length by rotating the cam ring. The group has a shape that can be moved, and the focusing function is impaired when the rotational position of the cam ring is changed on both sides. A step zoom lens camera comprising: an adjustment area for simply moving the focus lens group in the optical axis direction without using a lens; and a cam ring drive mechanism for pulse-controlling the rotation angle of the cam ring. 2. The step zoom lens camera according to claim 1, wherein the adjustment area of the cam ring is used to give the cam ring a rotation angle for performing zooming adjustment and fb adjustment. 3. The step zoom lens camera according to claim 1, wherein the variable power lens group comprises three groups, and an intermediate two group lens is a focus lens group also serving as the variable power lens group. .